The present invention relates to a white blood cell-removing device to be used in obtaining a blood product not containing white blood cells or other blood components contained in blood collected from a donor. The present invention also relates to a white blood cell-removing apparatus and a white blood cell-removing method for obtaining the blood product not containing white blood cells or other blood components contained in the blood collected from the donor.
Generally, the white blood cell-removing device has a housing; a white blood cell-removing filter provided to partition the inside of the housing into an inlet side blood chamber and an outlet side blood chamber; a blood inlet port communicating with the inlet side blood chamber; and a blood outlet port communicating with the outlet side blood chamber.
The white blood cell-removing device is used by connecting a tube provided at a blood inlet side with a tube of a container accommodating non-filtered blood and connecting a tube provided at a blood outlet side with a tube of a container accommodating filtered blood. White blood cells are removed by placing the container accommodating the non-filtered blood at an upward position, the container accommodating the filtered blood at a downward position, and the white blood cell-removing device at a position intermediate therebetween to introduce blood into the white blood cell-removing device by utilizing the vertical difference between the positions thereof. White blood cell-removed blood is accommodated in the container located at the downward position.
When the white blood cell-removing device has a construction containing much air therein, the air prevents a smooth flow of blood. To expel the air from the white blood cell-removing device, an air-removing operation is performed by placing the inlet side of the white blood cell-removing device at a downward position and the outlet side thereof at an upward position; and then, the white blood cell-removing device is turned upside down to perform a filtering operation.
A smooth filtration proceeds for a certain period of time after the blood filtering operation starts. But after a while, the filtering speed becomes very slow. Because the amount of unfiltered blood injected into the inlet side of the white blood cell-removing device is small immediately after the blood filtering operation starts, a low pressure is applied to a filtering material and thus the flow-down speed of the blood is not reduced. In the case of a white blood cell-removing device having a housing made of a soft material, shortly after blood more than an amount corresponding to the volume of the inlet side blood chamber is injected thereinto, the filtering material is pressed by the pressure of the blood which has been stored in the inlet side blood chamber. As a result, the volume of the outlet side blood chamber decreases and the filtering material contacts the inner surface of the housing made of the soft material. Consequently, the outlet side blood chamber is closed and the filtering speed becomes very slow.
As a container for collecting filtered blood, a soft blood bag is generally used. After the filtering operation starts, an initial flow of filtered blood flowing out from a white blood cell-removing device drops to a filtered blood collection container at a speed nearly equal to a free drop speed. This is because there are no factors which prevent the drop of the filtered blood below the white blood cell-removing device. But when the flow speed of the filtered blood is low at the outlet side of the filter, as described above, the filtered blood collection container acts as though it pulls the filtered blood thereto. As a result, the outlet side blood chamber of the white blood cell-removing device has a negative pressure, which allows the housing made of the soft material to contact the filtering material closely.
A long filtering time leads to deterioration of not only operability but also the quality of the blood product.
In order to solve such a problem, there is proposed a method of inserting a separate member, for example, a space-forming material or a rod into the outlet side blood chamber. But the insertion of the separate member may cause a defective adhesion of the material of the housing, which causes leak of blood.
The following method has been also adopted to obtain a blood product: an unprocessed blood filling container is connected with the blood inlet port of a white blood cell-removing device; a processed blood collection container is connected with the blood outlet port of the white blood cell-removing device; and the unprocessed blood filling container is placed at an upward position and the processed blood collection container is placed at a downward position to collect processed blood by gravity by the processed blood collection container.
But the above method has a problem that at the termination of the white blood cell-removing, it is impossible to collect blood remaining in the interior of the white blood cell-removing device, blood remaining in a tube between the white blood cell-removing device and the unprocessed blood filling container, and blood remaining in a tube between the white blood cell-removing device and the processed blood collection container.
Therefore, it is a first object of the present invention to provide a white blood cell-removing device not using a separate member to prevent defective adhesion of materials of a housing thereof and having a blood filtering speed which is reduced in a small extent.
It is a second object of the present invention to provide a white blood cell-removing apparatus and a white blood cell-removing method capable of obtaining much blood product from collected blood.